I've had both Mire frogs drop, one of the rats from Waterway, one of the whales from Redrocks (I gave it to someone in a g/g thread before den was a thing, which sucks because it was the purple one XD), one of the boars from Arena, both turtles from Crystal Pools, and one of the rocs from Harpy's.

My proudest is a toss up between the rat and the roc, since I spent so much time in the Mire, Pools, and Arena that I wasn't as surprised.

Looking at this thread I've had better luck than I thought I did.